Kuormanvakautusjärjestelmä hydraulista nosturia varten

The goal of this thesis is to design an anti-sway load control system for a hydraulic crane. In this thesis a tool which is connected to the crane by using two joints is studied. These joint can sway freely in two different directions so the tool includes 2DOF. The test crane in this thesis is Hiab 033 with 3DOF in the Cartesian space. At the beginning of this thesis the forward and the differential kinematics equations for the test system are defined. For the controller design a dynamic model of the tool need to be determined. In this thesis, the dynamic model is constructed by using Lagrangian dynamic formulation. The anti-sway control system includes two main parts. The first controller part is the state feedback controller, which defines reference velocity for the boom tip. From the tool only the swaying angles can be measured so in the control system need to be used estimator to construct missing state velocities. In this thesis state-feedback controller and the Kalman filter is tuned by using Linear-Quadratic-Gaussian method. This method combines the Linear-Quadratic-Regulator and Kalman filter. The control signals for the valves are calculated by using proportional controllers. In this thesis the quality of the anti-sway controller is tested by using two different load mass sizes and two different test paths. According to the results it can be noted that the control system can compensate the tool swaying when the tool sways forward/backwards. When the tool sways left/right the controller cannot compensate the swaying as efficiently due to the nonlinear flexibility of the swing joint. According to the results it can also be noted that the load mass does not affect the anti-sway load control system

Improving Automated Operations of Heavy-Duty Manipulators with Modular Model-Based Control Design

The rapid development of robotization and automation in mobile working machines aims to increase productivity and safety in many industrial sectors. In heavy-duty applications, hydraulically actuated manipulators are the common solution due to their large power-to-weight ratio. As hydraulic systems can exhibit nonlinear dynamic behavior, automated operations with closed-loop control become challenging. In industrial applications, the dexterity of operations for manipulators is ensured by providing interfaces to equip product variants with different tool attachments. By considering these domain-specific tool attachments for heavy-duty hydraulic manipulators (HHMs), the autonomous robotic operating development for all product variants might be a time-consuming process. This thesis aims to develop a modular nonlinear model-based (NMB) control method for HHMs to enable systematic NMB model reuse and control system modularity across different HHM product variants with actuators and tool attachments. Equally importantly, the properties of NMB control are used to improve the high-performance control for multi degrees-of-freedom robotic HHMs, as rigorously stability-guaranteed control systems have been shown to provide superior performance. To achieve these objectives, four research problems (RPs) on HHM controls are addressed. The RPs are focused on damping control methods in underactuated tool attachments, compensating for static actuator nonlinearities, and, equally significantly, improving overall control performance. The fourth RP is introduced for hydraulic series elastic actuators (HSEAs) in HHM applications, which can be regarded as supplementing NMB control with the aim of improving force controllability. Six publications are presented to investigate the RPs in this thesis. The control development focus was on modular NMB control design for HHMs equipped with different actuators and tool attachments consisting of passive and actuated joints. The designed control methods were demonstrated on a full-size HHM and a novel HSEA concept in a heavy-duty experimental setup. The results verified that modular control design for HHM systems can be used to decrease the modifications required to use the manipulator with different tool attachments and floating-base environments

Position-Based Impedance Control Design for a Hydraulically Actuated Series Elastic Actuator

publishedVersionPeer reviewe

Probabilistic Camera-to-Kinematic Model Calibration for Long-Reach Robotic Manipulators in Unknown Environments

In this paper, we present a methodology for extrinsic calibration of a camera attached to a long-reach manipulator in an unknown environment. The methodology comprises coarse frame alignment and fine matching based on probabilistic point set registration. The coarse frame alignment is based on the known initial pose and assists in the fine matching step, which is based on robust generalized point set registration that utilizes position and orientation data. Comparison with other methods utilizing only position data is provided. The first 6 DOF point set is obtained using a SLAM algorithm running on a camera attached near the tip of a manipulator, whereas the second point set is obtained using a kinematic model and joint encoders. Real- time experiments and a use case are presented. The results demonstrate that the proposed methodology is suited for the application, and that it can be useful in operations requiring precise visual measurements obtained near the tip of the manipulator.acceptedVersionPeer reviewe

Kuormanvakautusjärjestelmä hydraulista nosturia varten

The goal of this thesis is to design an anti-sway load control system for a hydraulic crane. In this thesis a tool which is connected to the crane by using two joints is studied. These joint can sway freely in two different directions so the tool includes 2DOF. The test crane in this thesis is Hiab 033 with 3DOF in the Cartesian space. At the beginning of this thesis the forward and the differential kinematics equations for the test system are defined. For the controller design a dynamic model of the tool need to be determined. In this thesis, the dynamic model is constructed by using Lagrangian dynamic formulation. The anti-sway control system includes two main parts. The first controller part is the state feedback controller, which defines reference velocity for the boom tip. From the tool only the swaying angles can be measured so in the control system need to be used estimator to construct missing state velocities. In this thesis state-feedback controller and the Kalman filter is tuned by using Linear-Quadratic-Gaussian method. This method combines the Linear-Quadratic-Regulator and Kalman filter. The control signals for the valves are calculated by using proportional controllers. In this thesis the quality of the anti-sway controller is tested by using two different load mass sizes and two different test paths. According to the results it can be noted that the control system can compensate the tool swaying when the tool sways forward/backwards. When the tool sways left/right the controller cannot compensate the swaying as efficiently due to the nonlinear flexibility of the swing joint. According to the results it can also be noted that the load mass does not affect the anti-sway load control system

Nonlinear Full-Model-Based Controller for Unactuated Joints in Vertical Plane

Articulated multiple degrees-of-freedom (DOF) hydraulic manipulators are used in many industry tasks. These hydraulic manipulators can be used to move heavy loads, such as logs and containers. The grasping tool of these manipulators is often connected at the tip of the manipulator by using unactuated revolute joints, which are not directly controllable. Currently, work performed efficiently by commercial hydraulic manipulators depends on the driver, and the automation level of these manipulators is relatively low. The Virtual Decomposition Control (VDC) is the nonlinear model-based control theory, which performs subsystem-based control design and stability analysis for complex multiple DOF redundant hydraulics manipulators. In this paper, we present a VDC approach based nonlinear full-model-based anti-sway controller for a redundant manipulator in vertical plane. The experimental results, with a full-size redundant hydraulic manipulator, verify that the proposed anti-sway control efficiently damps load swaying in the vertical plane motions.acceptedVersionPeer reviewe

Impedance Control of Hydraulic Series Elastic Actuator with a Model-Based Control Design

Traditional mechanical actuators are designed with a high stiffness, which increases the system bandwidth. The operation of stiff actuator in uncertain environments is a challenging task due to physical interactions with the environment. Series elastic actuators (SEAs) have become the prominent method for decreasing stiffness between power output shafts and the environment in electric torque-controlled light arm applications. Compared to lightweight arms, the hydraulic actuated SEAs (HSEAs) can provide a much higher power-to-weight ratio. However, the control design for an HSEA is a challenging task due to the high non-linear dynamics of hydraulic systems. In this study, a novel subsystem-dynamics-based controller for an HSEA is designed using the virtual decomposition control (VDC) approach as a framework. The designed controller is incorporated as an inner-loop controller for previously designed a novel impedance controller. The one degrees-of-freedom (DOF) experimental setup is used to verify the control performance of the proposed controller.acceptedVersionPeer reviewe

Real-time Distance Query and Collision Avoidance for Point Clouds with Heavy-duty Redundant Manipulator

This paper presents a real-time method for generating joint trajectories for redundant manipulators with collision avoidance capability. The coordinated motion control system of the heavy-duty hydraulic manipulator resolves joint references so that a goal position can be reached in real-time without any collisions. The proposed method is able to detect and prevent different types of possible collisions, including self-collisions and collisions with obstacles. When the control system detects the risk of collision, the collision server searches the points where the collision is about to occur and calculates the shortest distance between the colliding objects. The collision server is used to retain static point clouds and to calculate the shortest distance between objects that are too close to each other. The point clouds on the server are kept up to date with the manipulators' joint sensors and laser scanner-based measurements. During coordinated motion control, the joint trajectories of the redundant manipulator are modified so that the collisions can be avoided, while at the same time, the trajectory of the end-effector maintains its initial trajectory if possible. Results are given for a 4-DOF redundant heavy-duty hydraulic manipulator to demonstrate the capability of this collision avoidance control system.acceptedVersionPeer reviewe

Redundancy-based visual tool center point pose estimation for long-reach manipulators

In this paper, we study a visual sensing scheme for 6 degree-of-freedom (DOF) tool center point (TCP) pose estimation of large-scale, long-reach manipulators. A sensor system is proposed, designed especially for mining manipulators, comprising a stereo camera running a simultaneous localization and mapping (SLAM) algorithm near the TCP and multiple cameras that track a fiducial marker attached near the stereo camera. In essence, the TCP pose is formulated using two different routes in a co-operative (eye-in-hand/eye-to-hand) manner using data fusion, with the goal of increasing the system's fault tolerance and robustness via sensor redundancy. The system is studied in offline data analysis based on real-world measurements recorded using a hydraulic 6 DOF robotic manipulator with a 5 m reach. The SLAM pose trajectory is obtained using the open source ORB-SLAM2 Stereo algorithm, whereas marker-based tracking is realized with a high-end motion capture system. For reference measurements, the pose trajectory is also formulated using joint encoders and a kinematic model of the manipulator. Results of the 6 DOF pose estimation using the proposed sensor system are presented, with future work and key challenges also highlighted.Peer reviewe

3D Attitude Calculation for the Grasper of a Crane System with a Rotary Gyroscope

This paper focuses on attitude calculation for a grasper, which hangs on a heavy-duty machine with rope or links at the boom tip, using a triad-axis rotary gyroscope attached on the grasper. The aim of the attitude calculation is to provide anti-sway control. We try to decrease the drift of the gyroscope in two directions, except the rotation axis. The algorithm was validated on a test bed, which is based on a crane system. The test results show that with a rotary platform, long-term drift of the gyro decreased and the accuracy of angle integration for the grasper became better.acceptedVersionPeer reviewe